Don't ruin the vibe — let them talk about something cheerful.
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The image comes from Tang-era writers listing things that ruin a beautiful view — loud music, shabby inns, coarse talk. Yan Shu's 《煮茶》 keeps the phrase in literary currency: '未向人间杀风景，更持醪醑醉花前.'
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Very common in speech. Works for any mood-killer: bringing up work at a party, an accountant's reminder mid-celebration, rainy weather during a picnic.
